Evolution

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Evolution

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n November 24th, 1859 one of the most socially prominent science books was published.

It was entitled “On the origin of species by means of natural selection” and his author was Charles Darwin. In its pages he explained the life of all the organisms, including human beings, as a long process of gradual evolution, by means of which all the species are more or less biologically related. This year we commemorate the 150th anniversary of this publication and the 200 of the birth of its author.

The Aquarium Finisterrae joins the international commemoration of the Year Darwin with the inauguration of a set of modules on evolution

■ If, according to Darwin, humans descend from monkeys, why do monkeys exist?

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arwin did not say that humans descend from the monkeys or the current apes, but we have a common ancestor to them and to the rest of the primates. The chimpanzees, gorillas and orangutangs are not our grandparents but our cousins. These animals belong to other branches of our biological family, and the coexistence of different species with a common predecessor is very common in nature. All the primates descend from arboreal animals that lived 60 million years ago, they fed on insects, had frontal vision and had hands with an opposable thumb.

■ Which is the missing link of evolution?

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In fact there is not a single missing link, but many. For example, in 2004 it was discovered a fossil of Tiktaalik, an animal that lived 375 million years ago, which had characteristics of fishes (scales, gills) and amphibians (lungs, flexible neck). It was a transition between aquatic and terrestrial vertebrates. We call “missing links” to the old species that serve as an example of an evolutionary leap. So, it has a symbolic value, because to demonstrate the evolution it is not necessary to find fossil of hybrids between different species.

Two years after the publication of “On the origin of species” a fossil of Archaeopteryx was found. It was presented as the missing link that suggest the relationship between birds and reptiles. It had certain reptilian features (anatomy, teeth) and others from the birds (winged arms, feathers)

■ Are humans the most evolved species?

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uring all history, many human cultures considered us the chosen species. For that reason we tend to see us aside and over the rest of the animals, as if we were the top of an evolutionary pyramid or the last link of a progress chain. But the reality is quite another. The evolution is a process moved by the chance of the genetic mutations, so it does not have a pre-established objective. Evolution does not mean improvement nor progress, but adaptation to survive in the present conditions of the Earth, so no species are superior to others.

Nice postcards published by the Natural History Museum in Stuttgart (Germany)

■ Why does evolution happen?

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n a group every individual is slightly different. And those small differences make some be better equipped for survival and reproduction. If their descendants inherit those advantages, with time they can end up extending to all the population. Thus all the species arose. The key is in the random alterations of the DNA (genetic mutations), which are the ones in charge for the appearance by chance of slightly different individuals. Exceptional natural phenomena also take part in evolution (for example, meteorite impact).

The famous Dutch artist M. C. Escher (1898-1972) illustrated a peculiar evolutionary meeting between apes and humans

■ When did intelligence and speech turned up in the evolution of humans?

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ntelligence and speech are two human features that we flaunt. They’re considered as something very exclusive and that its appearance impelled human evolution.

Fossils and rest of our ancestors can not conclude when they began to speak, but make possible to suppose that they could do it. On the other hand, we know that chimpanzees can learn ways of communication very close to human language. And, with no doubt speech has a great value: it allows communication, knowledge and deep thought.

■ Did the neck of the giraffes grow to reach higher leaves of the trees?

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ome naturalists from the 19th century believed that the long neck of the giraffes would be the turn out of the efforts made during generations to reach the treetops. But living beings do not evolve according to their own interest or needs. Darwin explained that it was chance that caused some giraffes to have a longer neck. And that natural selection favoured the survival of the more and more long-necked giraffes. Less clear is that reaching higher leaves was the reason for their success.

■ Does natural selection cause the survival of the strongest and therefore the improvement of the species?

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ometimes the better adapted are the strongest, but in other cases they can be those that run faster, those that crouch better or, simply, the most fertile. As physical strength normally requires higher food consumption, it can even be a disadvantage for the survival during shortage periods. Natural selection chooses the features from the best survivals, which in addition are the ones that reproduce and transmit those features to their descendants, whichever they are.

■ Will we keep evolving? How will humans be in the future?

■ If there is evolution, why are there in our body things that we do not need or that are hinders? (For example: wisdom teeth, blue eyes, or nipples in the males)

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■ How do we know that our ancestors come from Africa? s new fossils come out, the genealogy tree of the hominids, which are the biological family to whom the human species belongs, is reconstructed. Darwin predicted the African origin of the human species. This was demonstrated with the genetic studies and the appearance in Africa of many fossils of our evolutionary lineage (Australopithecus, Homo habilis, etc.).

urrent species are the result of an adaptation process to the conditions of life that were changing from the origin of the Earth. For example, the climate changed a lot from the era of the dinosaurs and will keep changing. New species will arise and others will be extinguished. Evolution will go on for all the species, including ours. As evolution is a process in which chance and the unexpected play a main role, it is impossible to predict how will humans be in the future or when will we be extinguished.

iving beings keep certain features of our ancestors although they no longer act specially. For example, hen wings or wisdom teeth. Natural selection chooses the characteristics that give advantage at a certain moment, but does not eliminate the useless ones, and that demonstrates that there is not an objective to improve or to perfect species.

We have many features that are not the result of an adaptation.

Sometimes useless features, like nipples in Pelvis Femur male mammals, remain because they are linked in the genes to other Many snakes keep vestiges of bone features that are essenstructures where their ancestors used to tial indeed. have legs

■ What are the living fossils?

Experiment on evolution

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arwin discovered that the species evolve at different speed.

Some change in just a short time, but there are other species that remain almost unaltered for many million years: they are called the living fossils. Among them are the crocodiles, the nautilus, the ginkgo or the coelacanth. The coelacanth was supposed to be extinguished for over 65 million years, until in 1938 a living specimen was catch. That fish was quite similar to the fossils of its ancestors of the Cretaceous!

Interval of 5 generations with no selection

Number of chaetas 56 52 48 44 40 36 32 28

Nautilus is a living representative of a group of animals that came up 600 million years ago and had hardly changed

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Selection of individuals with the higher number of chaetas Selection of individuals with the lower number of chaetas

■ Virus are the simpler living beings: are they the less evolved?

This chart shows the variation in the number of chaetas- rigid bristles- in consecutive generations of vinegar flies depending on the reproductive individuals selected.

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n order to say that a species evolved more than another one it is necessary to look for an objective criterion. For example, which one accumulated more changes in its evolution from the last common ancestor next to both species?

Considering all the species, those that evolved more are indeed some of simplest: the bacteria reproduce at high speed, accumulating mutations to a rate much greater than the most complex organisms.

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Fly generations

■ That of Darwin is a theory but, actually, are scientists sure of the evolution of the species?

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es. Scientists found evidences for the evolution in fossils, in the anatomic comparison and in the genes of different species. And if there still were doubts, they also observed the evolution in populations of bacteria, fishes and insects “live”. Thanks to the evidences and to direct observations, the evolution can no longer be questioned: it is a scientific fact as demonstrated as the rotation of the Earth or the existence of atoms. However the theory that explains the evolution can be improved and extended.

■ What is the theory of evolution good for?

Escherichia coli bacteria

■ How did Darwin discover evolution?

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everal naturalists had already defended the evolution before Darwin. But he was the first able to explain it.

During his trip around the world he compiled several examples of how life seemed to adapt to its environment. That experience, and the reading of Lyell’s book “Principles of Geology” made him be convinced by his return to England, that the species change, but he did not understand the mechanism of these changes. Finally, he was able to explain it in 1838, when he reached the idea of natural selection. He was inspired by farmers who selected the best varieties and also by the ideas of Thomas Malthus on the competition for the resources in the fight for survival.

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irst it serves to understand history of life in our planet and also to know how species change in relation to their natural environment. Something very important, as the conservation of biodiversity is fundamental for human civilization. And, in addition, the knowledge of the evolutionary processes inspires practical applications in public health (better vaccines), in police investigations (changes in the DNA) and in the optimization of technological designs (bridges, computer programs, communication networks).

Darwin studied the variation of the species (specifically pigeons) by artificial selection. The image shows the original type –in the centre- and the different variations obtained by breeding selection

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■ Where did Darwin go wrong?

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arwin discovered the main engine of evolution: the natural selection, although he did not understand how it worked. He couldn’t explain three important things: how do appear the new features that differentiate individuals, how those features are inherited favoured by natural selection, and how are they extended by every population of a species. The theory of evolution by natural selection was incomplete until, by the middle of the 20th century, the investigations in genetics allowed to solve those doubts (and to consider new questions).

■ 17 Could God create life by evolution?

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here are no scientific tests to prove divine intervention in evolution … although the opposite cannot either be demonstrated. Science does not take care of this kind of questions, it only investigates facts and processes that can be observed, measured or reproduced. Religious beliefs are out of scientific research.

Cover of the magazine TIME

■ Are humans changing the course of evolution?

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volution is the result of the adaptation to natural environment. And as humans have the capacity to alter the environment, there is no doubt that we are conditioning the evolution of many organisms and bringing about the extinction of species. Human impact in our environment will also change our own evolution. Nevertheless, human technology (clothes, housing, etc) allows our adaptation to certain changes without modifying our nature.

The dodo was a bird endemic to the island of Mauritius, extinguished due to humans by mid 17th century)

■ Are there human races more evolved than others?

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n fact it was discovered a long time ago that the human races do not exist. The differences between the diverse ethnic groups do not have biological relevance. Genetically black and a white can look more alike that two black or two white to each other. Every human are equal evolved.

Acceptance of the Theory of Evolution This was a study, developed in 2005 to illustrate the popular acceptance of evolution in different countries.

■ Does every living being come from a unique ancestor?

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cience has evidences that every present species has a common ancestor: for example, the fact that all the living beings on Earth have the same genetic code. There are data that locate the origin of life 3,500 million years ago. And according to current knowledge, the first living organisms could be a type of very simple bacteria.

■ After 150 years, was Darwin’s theory old fashioned before the new scientific advances?

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arwin demonstrated that the evolution is a fact and discovered that natural selection is the main engine of evolution. Those are his two major scientific contributions and nowadays they are more effective than ever.

Other ideas of his theory were improved and completed thanks to new investigations. Also new data arose that maintain an open debate on some details, as it happens to all the scientific theories.

■ Is the theory of evolution banned in any country? Did Darwin have problems of censorship and lack of understanding?

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ome scientific discoveries cause rejection because they contradict ideas or very based interests. This happens to the theory of evolution. In many countries, including Spain, its teaching was prohibited for decades. Today the battle continues in the

United States, where there are very active antievolutionist groups. In fact, a new film on Darwin had problems to be released there in 2009. And, also during the Year Darwin, an article on his figure was censured in a Turkish scientific magazine.

Censured cover of the Turkish magazine “Science and technology” next to the published one

Darwin’s ideas were satirize by many cartoonists as a reflection of the social rejection they caused

Museos Científicos Coruñeses

Charles Darwin

(February 12, 1809 – April 19, 1882)

H

e is one of the most prominent scientists of history.

He showed an early vocation by natural science, in which, besides important contributions, he brought about a revolution. Today it is considered that the evolution of life and the human being is a scientific fact, and that its main mechanism is natural selection.

■ The voyage of the Beagle The most fundamental event in the life of Charles Darwin was his trip on the Beagle, a five-year marine journey in

Darwin after finalizing his trip on board of the Beagle

This was his appearance when he published "On the Origin of Species by Means of Natural Selection"

In the last years of his life

At the age of 22 Darwin embarked on the HMS Beagle, to make a trip around the world that lasted from 1831 to 1836

Museos Coruñeses animals, fos(wild and domestic natureCientíficos which he studied the sils, plants, etc) of different places in the world. The experiences, studies, readings and reflections put him in the way to develop his ideas on evolution.

■ The origin of species After 23 years of reflections, experiments and other works Charles Darwin published his ideas in the book “The origin of species by natural selection”. The main reason for this edition was the reception of a letter from a young naturalist, called Wallace, in which he presented certain ideas on the evolution of Museos Coruñeses to hisCientíficos own. Darwin avoided in his writing life which were similar any reference to the human being, but the social controversy caused by his theory made this subject gain prominence. Many understood that their words contradicted those of the Bible and the divine origin of the human being.

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